Magnetic recording medium

Abstract

A magnetic recording medium that does not develop film swelling when exposed to severe conditions has a nonmagnetic substrate having a trench formed in the area within 2 mm from and concentrically with the outer circumference or the inner circumference of the nonmagnetic substrate, or formed outside the data area concentrically with the outer circumference or the inner circumference of the nonmagnetic substrate.

What is claimed is:  
     
       1. A magnetic recording medium comprising: 
       a nonmagnetic substrate made of a plastic resin, the nonmagnetic substrate having a trench extending along the vicinity of an edge of the nonmagnetic substrate;  
       a nonmagnetic undercoating layer on the nonmagnetic substrate, the non magnetic undercoating layer coating the trench;  
       a magnetic layer on the nonmagnetic undercoating layer;  
       a protection layer on the magnetic layer; and  
       a liquid lubricant layer on the protection layer.  
       wherein said medium having a substrate with said trench exhibits reduced swelling caused by absorbed moisture compared to a medium having a substrate without said trench.  
     
     
       2. The magnetic recording medium according to  claim 1 , wherein the trench is from 0.1 μm to 1.0 μm in width and 100 nm or deeper in depth. 
     
     
       3. The magnetic recording medium according to  claim 1 , wherein the trench is 0.5 μm in width and 100 nm or deeper in depth. 
     
     
       4. The magnetic recording medium according to  claim 1 , wherein the trench is in the area within 2 mm from the edge of the nonmagnetic substrate. 
     
     
       5. The magnetic recording medium according to  claim 1 , wherein the trench is outside the data area of the nonmagnetic substrate. 
     
     
       6. A method of manufacturing a magnetic recording medium including a nonmagnetic substrate; a nonmagnetic undercoating layer on the nonmagnetic substrate; a magnetic layer on the nonmagnetic undercoating layer; a protection layer on the magnetic layer; and a liquid lubricant layer on the protection, layer the method comprising the steps of: 
       providing the nonmagnetic substrate composed of plastic;  
       forming a trench extending along the vicinity of an edge of the plastic substrate; and  
       forming the nonmagnetic undercoating layer on the nonmagnetic substrate, the nonmagnetic undercoating layer coating the trench.  
       wherein said medium having a substrate with said trench exhibits reduced swelling caused by absorbed moisture compared to a medium having a substrate without said trench.  
     
     
       7. The method according to  claim 6 , wherein the step of forming comprises forming the trench from 0.1 μm to 1.0 μm in width and 100 nm or deeper in depth. 
     
     
       8. The method according to  claim 6 , wherein the trench is 0.5 μm in width and 100 nm or deeper in depth. 
     
     
       9. The method according to  claim 6 , wherein the step of forming comprises forming the trench in the area within 2 mm from the edge of the nonmagnetic substrate. 
     
     
       10. The method according to  claim 6 , wherein the step of forming comprises forming the trench outside the data area of the nonmagnetic substrate. 
     
     
       11. A magnetic storage device comprising: 
       a magnetic recording medium mounted thereon, the magnetic recording medium including:  
       a nonmagnetic substrate made of a plastic resin, the nonmagnetic substrate having a trench extending along the vicinity of an edge of the nonmagnetic substrate;  
       a nonmagnetic undercoating layer on the nonmagnetic substrate, the non magnetic undercoating layer coating the trench;  
       a magnetic layer on the nonmagnetic undercoating layer;  
       a protection layer on the magnetic layer; and  
       a liquid lubricant layer on the protection layer.  
       wherein said medium having a substrate with said trench exhibits reduced swelling caused by absorbed moisture compared to a medium having a substrate without said trench.